The field of the invention is that of electrostatic chucks for holding a workpiece by electrostatic attraction between the workpiece and one or more electrodes in the chuck.
Extensive work has been done in electrostatic chucks within the last ten years. An example is the chuck illustrated in U.S. Pat. No. 5,055,964, issued to the International Business Machines Corporation.
A chuck adapted to avoid a problem in the prior art of excessive retention of clamping force after power is removed is illustrated in U.S. Pat. No. 5,103,367. That chuck uses an alternating current to avoid polarization of the dielectric.
The invention relates to an electrostatic chuck that suppresses the formation of vacuum arcs between the back of the wafer being processed and the body of the chuck by the interposition of a conductive guard ring that floats close to the self-bias potential induced by the plasma on the wafer, thereby defining an equipotential area between the closest electrode and the wafer and capacitively dividing the voltage between the wafer and the closest electrode.